In Vitro Neutral Detergent Cellulase Method and Chemical Composition to Predict In Vivo Fermentable Organic Matter of Roughages

SIMPLE SUMMARY: Various methods such as in situ, gas production and enzymatic methods are exercised to estimate the in vivo fermentable organic matter (FOM). However, each of these methods has its limitations. The in vivo method with fistulated animals for FOM determination is expensive, laborious and negatively affects animal welfare. Similarly, the in situ method also requires rumen fluid and is costly. However, enzymatic methods eliminate the need for fistulated animals and are comparatively simple, cheaper, faster, have greater repeatability, and also ensure the standardization of the process. Additionally, in situ technique can be disregarded as a standard method to test the accuracy of other techniques in cases where in vivo testing is not feasible. Therefore, in the current study, we compared the in situ nylon bag technique with the in vitro neutral detergent cellulase method and chemical composition to estimate in vivo FOM of roughages. ABSTRACT: In Vivo fermentable organic matter (FOM) reflects the energy production and the potential of rumen’s microbial protein synthesis. However, the in vivo method with fistulated animals for FOM measurement compromises animal welfare and is laborious as well as expensive. Although the alternative in situ nylon bag technique has been widely used, it is also costly and requires rumen liquor. Therefore, the present study was performed to compare the in situ nylon bag technique with the in vitro neutral detergent cellulase (NDC) method or chemical composition to estimate in vivo FOM of roughages. For this purpose, we selected 12 roughages, including six each from forages and crop residues. Our results have shown the strong correlation equations between FOM(in situ) and FOM(NDC) of forages (n = 6; R(2) = 0.79), crop residues (n = 6; R(2) = 0.80), and roughages (n = 12; R(2) = 0.84), respectively. Moreover, there were also strong correlations between the chemical composition of roughages and FOM(in situ) (n = 12; R(2) = 0.84–0.93) or FOM(NDC) (n = 12; R(2) = 0.79–0.89). In conclusion, the in vitro NDC method and chemical composition were alternatives to in situ nylon bag technique for predicting in vivo FOM of roughages in the current experiment.